Hydraulic cushioning device



July 9, 1968 J SPENCE ET A.

HYDRAULIC CUSHIONING DEVICE 3 Sheets-Sheet 1 Filed June 27, 1966 IN VE NTORS JOHN H. SPENCE MERRIL L 6. MA RSHA LL July 9, 1968 SPENCE ET AL3,391,798

HYDRAULIC CUSHIONING DEVICE Filed June 27. 1966 5 Sheets-Sheet 2 E: asl2 #1 g 5.. INVEN TORS JOHN H. SPEN CE MERRILL a. MARSHALL y 9, 1968 H.SPENCE ET AL 3,391,798

HYDRAULI C CUSHION I'NG DEVICE Filed June 27. 1966 5 Sheets-Sheet 3 INVE N TO RS JOHN H SPENCE MERRILL G. MAIiSHALL BY %M A ATT'Y.

United States Patent 3,391,798 HYDRAULIC CUSHIONING DEVICE John H.Spence, Chicago Heights, and Merrill G.

Marshall, Homewood, IlL, assignors to Pullman Incorporated, Chicago,111., a corporation of Delaware Filed June 27, 1966, Ser. No. 560,712 12Claims. (Cl. 21343) ABSTRACT OF THE DISCLOSURE In a hydraulic cushiondevice having an open end cylinder with a stop head and movable pistontherein, a piston mounted reservoir closing the cylinder open end,passage means between the closed end of the cylinder and the reservoir,and a return spring between the piston and the cylinder, the improvementcomprising snubber stop means in the cylinder for cushioned engagementwith the cylinder head comprising a reciprocably movable piston mountedsnubber member engageable with said cylinder head upon outward pistonmovement, a fixedly piston mounted snubber member engageable with themovable member upon outward piston movement, and biasing means betweenthe movable member and the piston urging said movable member away fromthe fixed member.

The present invention relates to hydraulic cushioning devices and moreparticularly to an improved hydraulic cushion device of the type whichmay be used in cushion underframe railway cars for providing car bodyand lading protection.

A hydraulic cushion of the type to which the present invention relatesis disclosed in US. Patent 3,218,052. The hydraulic cushion unitcomprise generally a hydraulic fluid filled cylinder in which there isreciprocally disposed a fluid displacement means which may be in theform of a piston head having fixed to one face thereof one end of atubular piston rod. The tubular piston rod extends through anintermediate cylinder head fixed inwardly of an open end of thecylinder. Fixed to the outwardly extending end of the cylinder is a baseplate against which there abuts one end of a return spring means. Theother end of the return spring abuts against a second base plate whichis fixed to and closes off the other end of the tubular piston.

The cylinder and fluid displacement means are movable between a neutralextended and contracted position. During the extension and contractionof the cushioning unit, hydraulic fluid flows between a high pressurechamber defined between the forward face of the piston head and theclosed end of the cylinder, and a low pressure chamber defined betweenthe rear face of the piston head and the intermediate cylinder head.

A flexible reservoir is attached between the intermediate cylinder headand the outwardly extending end of the piston rod. The reservoircommunicates with the low pressure chamber via fluid passages throughthe cylinder head and serves to receive hydraulic fluid displaced by thepiston rod during the contraction of the cushion unit.

The hydraulic cushion unit is preferably of the type having anapproximately constant resisting force travel characteristic. To thisend, the piston head is provided with an orifice which is aligned withthe piston rod bore having ports providing fluid communication with thelow pressure chamber. Extending through the orifice is a metering pinwhich is constructed so as to vary the fluid flow through the orifice ina manner achieving the approximate substantially constant resisting orcushioning force during each increment of the travel of the cushioningunit from the extended to contracted position. The metering 3,391,798Patented July 9, 1968 "ice pin is fastened at one end to the base plateso as to form a fluid tight seal.

The cushion unit is generally interposed between a sliding sill and anunderframe so as to cushion the forces imposed upon the car body and thelading carried thereon. In operation, the cushioning unit is disposedbetween a pair of stops which are fixed to the sliding sill and the carunderframe so that upon the imposition of a force to the sliding sillthe cushion unit is contracted from its extended position and duringthis time serves to absorb and dissipate a portion of the impact energyof the draft or buff force applied at the couplers. After the force ofthe impact has been dissipated the return spring is operative to returnthe cushion unit to its neutral or extended position. Under someconditions the sliding sill may stick within the support on theunderframe after the force has been dissipated. Under these conditions,the return spring is completely compressed so that when an impact isagain applied on the extended end of the sill, the full force of theimpact and the extension force of the spring is imposed on thecushioning unit. Thus, when the cushioning unit returns to its neutralposition, the forces of the impact and the spring force createconsiderable stresses on the cushioning components, particularly on thebase plate fixed to the tubular piston rod so that the base plate may beseparated from the piston rod.

It is a principal object of the present invention to provide anarrangement for reducing the possibility of failure of the cushion unitby separation of the base plate from the tubular piston rod.

To this end there is provided a snubber arrangement for applying asnubbing force which is effective to reduce the stresses on the cushionunit as the latter returns from its compressed to extended neutralposition.

Further objects and features will hereinafter appear.

In the drawings:

FIG. 1 is a cross sectional view of a cushion unit in the extendedneutral positional thereof and embodying the snubbing arrangement of thepresent inveintion;

FIG. 2 is similar to FIG. 1 but showing the hydraulic cushion unit inits contracted position;

FIG. 3 is a fragmentary sectional view of the cushion unit and showingin particular the position of the components of the snubbing arrangementas the cushion unit returns from the compressed to extended position;

FIG. 4 is a view similar to FIG. 3 but showing the position of thecomponents of the snubbing arrangement in the fully extended position ofthe cushion unit;

FIG. 5 is a view similar to FIG. 4 but showing the components of thesnubbing arrangement immediately prior to becoming operative to providea snubbing force as the cushion unit approaches the extended position.

FIG. 6 is a fragmentary sectional view of hydraulic cushion unit havinga modified fluid displacement means and showing a further modificationof a snubbing structure with the components thereof shown in theposition immediately prior to obtaining the snubbing action; and

FIG. 7 is a fragmentary sectional view similar to FIG. 6 but showing thecomponents of the snubbing structure in the extended neutral position ofthe cushion unit.

Referring now to the drawings, there is shown a hydraulic cushion unitor device 10 embodying the snubber arrangement 2% of the presentinvention. The hydraulic cushion unit it comprises generally a hydraulicfluid filled cylinder 11, a fluid displacement means 12 reciprocalwithin the cylinder 11, a flexible reservoir in the form of a boot 13which is suitably connected at one end to the cylinder 11 and at theother end to the fluid displacement means 12, a metering pin 14 forcontrolling the fluid flow from a high pressure chamber 15 to a lowpressure chamber 16, and return spring means 17 disposed between thecylinder 11 and the fluid displacement means 12.

The cylinder 11 includes a cylindrical tube 18 formed of steel or thelike to one end of which there is fixed as by welding 21 base plate 19which is of larger diameter than the cylindrical tube 18 to provide aprojecting ledge 21.

Disposed within the cylinder bore 22 and inwardly of the open end of thetube 18 is an intermediate cylinder head'24 having an axial opening 26.The intermediate cylinder head 24 may be suitably fixed within the bore22 by means of snap rings 27 seated within grooves formed within theperiphery of the bore 22.

The fluid displacement means 12 includes the piston head 28 which isreciprocal within the cylinder bore 22 and defines on the closure plateside thereof the high pressure chamber 15 and on the intermediatecylinder head side the low pressure chamber 16.

Seated within a groove formed in the periphery of the piston head 28 isa guide and sealing ring 29 which is preferably formed of a laminatedphenolic resin. The guide and sealing ring 29 is constructed so that theouter guiding surface thereof extends beyond the outer periphery of thepiston head 28 and thereby precludes metal to metal contact with thecylinder wall.

Fixed to the piston head 28 as by welding is one end of a tubular pistonrod 31 which extends through the axial opening 26 and defines therewithan annular passage 32 through which the hydraulic fluid flows from thelow pressure chamber 16 to the boot or reservoir 13 upon contraction andextension of the cushion unit 10.

As shown in particular in FIG. 1, a second follower or base plate 33 isconnected to the outer end of the tubular piston rod 31. In order tofixedly secure the base plate 33 to the tubular piston rod, a fasteningplug 34 is inserted into the end of the piston rod bore 35 and fixedtherein as by welding. The end of the piston rod bore 35 may be slightlyenlarged so that fastening plug 34 seats against a shoulder 36. At theterminal end the fastening plug 34 is fixed within the bore as bywelding.

' The base plate 33 is formed on its inner face with a recess 37 whichsnugly receives the terminal end of the piston rod 31. On its outer facethe base plate 33 is formed with a circular recess 38 which accommodatesthe head 39 of the bolt 41.

The piston head 28 is reciprocal within the cylinder bore 22 andincludes an axial orifice 44 through which the hydraulic fluid flowsbetween the high pressure chamber 15 and the low pressure 16 via thepiston rod bore 35 and an array of ports 46 formed in the piston rodadjacent the piston head 28.

As shown in particular in FIGS. 3-5, the forward or high pressure faceof the piston head 28 is formed with a circular recess 51 in which thereis disposed a flap valve ;52. The flap valve 52 is movable from aposition overlying a plurality of angularly spaced openings 53 formed inthe piston head 28 to a position spaced therefrom against the snap ring54. The flap valve 52 serves as a means for providing fluidcommunication between the low pressure chamber 16 and the high pressurechamber 15 during the return stroke of the cushion device from thecontracted position shown in FIG. 2 to the extended position shown inFIG. 1.

Extending through the axial orifice is the metering pin 14 which isfixed at one end to the base plate 19. The metering pin is formed withflutes 57 which serve to Vary the volume or flow of liquid through theorifice 44 in a manner imparting a substantially constant force travelcharacteristic as the cushion unit moves from its extended to thecontracted position upon the imposition of an impact to the base plates33 or 19. For a more complete description of the construction of themetering pin, reference is made to Peterson patent U.S. Patent3,218,052.

Limiting the movement of the cushion device 10 to its extended positionis the snubber arrangement 20 which serves as a stop to prevent afurther extension of the cylinder 11 and fluid displacement means 12against the force of the return spring 17 which is disposed between thebase plates 33 and 19. The return spring 17 may be a single spring or aplurality of springs arranged in tandem as shown.

The snubber arrangement 20 includes a snubber cylinder 61 having an openend 62 and a closed end 63 formed with an opening 64 through which thereslidably extends the piston rod 31. In the neutral extended position, asshown in FIGS. 1 and 4, the snubber cylinder 61 engages the inboard faceof the intermediate cylinder 24 and compresses a compression spring 65disposed between the end walls 66 of the cylinder 61 and the first stopring 67 fixed to the piston rod 31. Fixed to the piston rod 31 is apiston ring stop 68 which in the extended position of the cushion unit,as shown, seats within the bore 69 of the snubber cylinder 61 with theoutboard face abutting against the inner end wall 71 of the cylinderbore 69. In this manner the piston ring stop serves as a stop to limitthe lengthwise movement of the cylinder 11 and fluid displacement means12.

When the cushion unit moves from its extended to contracted position thebiasing spring 65 of the snubber arrangement 20 is operative to slidethe snubbing cylinder 61 lengthwise of the rod into abutting engagementwith a second stop ring 70 fixed to the piston rod 31 and spacedlengthwise of the first stop 67. However, when the piston rod 31 andcylinder 11 return toward the extended position under the force exertedby the return spring 17, upon contact of the intermediate cylinder head24 with the snubber cylinder 61, the latter is moved away from the stop70 against the force of the snubber spring and is slid lengthwise of thepiston rod 31 toward the stop 67 as shown in FIG. 4. During thismovement of the snubber cylinder 61, the piston stop ring 68 enters thecylinder bore 69. Thus, pressure force of the hydraulic fluid within thebore 69 is increased and thereby creates a resisting force which formsin the nature of a snubbing action which absorbs a portion of the energyand reduces the stresses imposed on the bolt 42, fixing the base plate32 to the piston rod 31. When the piston stop 68 strikes the inner wallor shoulder 71 of the bore 69, the unit is held in its neutral extendedposition by way of the force of the return spring 17 acting between thebase plates 19 and 33.

Referring now to FIGS. 6 and 7, there is shown a snubber arrangementincorporated in a cushion unit 101 having a modified fluid displacementmeans 102. In all other respects the structure of the cushion unit 101is identical to that described in connection with FIGS. 1-5 and,accordingly, like parts are designated the same.

The fluid displacement differs essentially in that the piston headassembly 103 is formed as a casting including a head 104, from whichthere extends a hollow shank 106 having a bore 107. Fixed to the end ofthe shank 106 within a recessed .groove is one end of the tubular pistonrod 31 with the bore 35 axially aligned with the shank bore 107. Theshank 106 is formed at its outer end with an enlarged rim 108 which isspaced from the piston head 104. The rim 108 serves as a stop andsnubber piston ring as more fully to be explained hereafter.

The piston head 104, similar to the piston head 28 of the embodimentshown in FIGS. 1-5, may be formed with an axial orifice 109 throughwhich there extends the metering pin 14. Formed on the forward or highpressure face is a circular recess 111 in which there is located a flapvalve which is movable from a position overlying a plurality ofangularly spaced openings 113 to a position spaced therefrom against asnap ring 116. The flap valve 112 serves to permit fluid communicationbetween the low pressure chamber and the high pressure chamber 15 duringthe return of the cushion unit from the contracted to extended position.

Providing fluid communication between the piston rod bore 35 and the lowpressure chamber 16 are ports 117 formed in the shank 106. Thus, uponcontraction of the cushion unit 10 from the extended neutral positionupon impact at either of the base plates 19 or 33, the hydraulic fluidwithin the high pressure chamber 15 via the orifice 109, shank bore 107and ports 117 flows into the low pressure chamber 16. The flow throughthe orifice 119 is controlled by the flutes 57 in the metering pin 14 toimpart a substantially constant force travel characteristic to thecushion unit 101.

Upon dissipation of the impact energy, the return spring 17 is operativeto return the fiuid displacement means 109 and the cylinder to theneutral position. As the unit 191 approaches the neutral position, thesnubber arrangement 120 is operative to reduce the impact of the stoprim 108 when the latter reaches its limit position against theintermediate cylinder head 24.

The snubber arrangement 120 includes a snubber cylinder 121 having aclosed end 122 formed with an opening 123 through which the piston rod31 slidably extends. The other end of the snubber cylinder is open andabutting against a rim 124 is one end of a spring 126 of which the otherend abuts against a stop ring 127 fixed to radially spaced ribs 128 onthe piston head casting. The spring 126 serves to normally bias thesnubber cylinder 121 against a stop ring 129.

As the cushion unit 181 approaches the neutral position the outboardface of the snubber cylinder 122 strikes the intermediate cylinder head24 whereupon the snubber cylinder 121 slides along the piston rodagainst the force of the biasing spring 126. Of course, during this movement of the snubber cylinder 121, the piston rod continues to move inthe direction of the arrow as shown in FIG. 6 so that the stop rim 108enters the snubber cylinder bore 131 causing an increase in pressureforces therein which resist the movement of the piston rod 31. In thismanner the relative acceleration forces of the piston rod 31 andcylinder 18 are reduced so that when the stop rim 108 strikes the innerwall 132 of the snubber cylinder bore 131, the stresses imparted throughthe length of the piston rod 31 to the base plate fastening bolt 39 arematerially reduced.

What is claimed is:

1. In a hydraulic cushion device comprising a hydraulic fluid filledcylinder, a first base plate fixed to one end of said cylinder, anintermediate cylinder head fixed within the bore of said cylinderinwardly of the open end thereof, first fluid displacement meansincluding a piston head reciprocable within said cylinder bore formovement between said base plate and said intermediate cylinder head toand from an extended position and a contracted position and a tubularpiston rod fixed at one end to said piston head and extending throughsaid intermediate cylinder head outwardly of said open end of saidcylinder, a flexible boot fixed between said intermediate cylinder headand said outwardly extending end of said tubular piston rod, hydraulicfluid passage means through said intermediate cylinder head providinghydraulic fluid communication between said cylinder bore and saidflexible boot, a second base plate fixed to said outwardly extending endof said tubular piston rod, return spring means interposed between saidfirst and second base plates, an axial orifice through said piston headproviding hydraulic fluid communication with said bore, port means insaid fluid displacement means providing hydraulic fluid communicationbetween the piston rod bore and said cylinder bore, a metering pin fixedto said second base plate for metering the flow of the hydraulic fluidthrough said orifice, the improvement comprising stop means for limitingthe extended length of said cylinder and second fluid displacement meansincluding a snubbing cylinder means slidably mouted on said piston rodand positioned between said piston head and said intermediate cylinderhead, said cylinder means having a closed end and an open end, a pistonring stop means fixed to said first fluid displacement meaus for entryinto said cylinder means, and biasing means yieldably holding the openend of said cylinder means displaced outwardly of the piston ring stopmeans, said snubbing cylinder means being located on said piston rod soas to be displaced over said piston ring stop means when said firstfluid displacement means and said cylinder reach said extended positionfrom said contracted position thereby to provide a hydraulic snubbingforce.

2. The invention as defined in claim 1 wherein a first stop ring and asecond stop ring are fixed to said second fluid displacement means formovement therewith in lengthwise spaced relationship, said closed end ofthe snubbing cylinder means being eugageable with said first stop ring,and said spring biasing means extending between said second stop ringand said snubbing cylinder means to yieldably retain the latter inengagement with said first stop ring.

3. The invention as defined in claim 1 wherein said piston ring stopmeans is located on said fluid displacement means between saidintermediate cylinder head and said piston head so that upon engagementof said snubbing cylinder means with said intermediate cylinder headsaid snubbing cylinder means moves lengthwise of said piston rod againstthe force of said biasing spring and said piston ring stop means enterssaid snubbing cylinder means.

4. The invention as defined in claim 1 wherein said ports in said fluiddisplacement means are formed in said piston rod, and said stop means isdisposed on said piston rod in proximity of said ports.

5. The invention as defined in claim 2 wherein said piston head isformed as a casting including a hollow shank having said ports formedtherein, said first stop ring being fixed to said piston rod and saidsecond stop ring to said piston head shank, and wherein said piston ringstop means is formed on said shank.

6. In a cushion device having a cylinder with an intermediate pistonstop cylinder head and a closed end, fluid displacement means includinga reciprocable piston rod havig a piston head movable between thecylinder head and the closed end and being extendable out of thecylinder, at rservoir coupling with the cylinder head and the portion ofthe piston rod extendable out of the cylinder, means including passagemeans inthe piston head and piston rod and cylinder head to providecommunication on either side of the piston head and between the pistonrod and the reservoir during expansion and contraction of the device,and resilient means being disposed between the fluid displacement meansand the cylinder for expanding the device to an extended positionsubsequent to compression of the device to the contracted position, theimprovement comprising a snubber stop arrangement adapted for engagementwith the cylinder head and comprising a movable snubber memberreciprocably mounted on the piston rod between the piston head and thecylinder head and adjacent the cylinder head, said movable snubbermember having one side adapted for engagement with said cylinder headupon outward extension of the piston rod with respect to the cylinder, afixed snubber member mounted on the piston rod on the other side of themovable snubber member and adatped for engagement with the movablesnubber member upon relative movement of the piston rod outwardly of thecylinder attendant to compressing any fluid between the movable andfixed members to retard movement of the fixed member toward the movablemember for snubbing the impact of the stop arrangement on the cylinderhead, and biasing means fixed bei tween the movable member and thepiston head and urging said movable snubber member away from the fixedsnubber member toward said cylinder head and urging said piston rodtoward the closed end of said cylinder.

7. The invention according to claim 6, and sad movable snubber memberhaving a recessed portion to receive said fixed member upon moving ofthe movable 7 member to the fixed member to compress any fluid betweenthe members.

8. The invention according to claim 7, and said movable member being anannular member having an annular recess about the piston member and saidfixed member being a ring receivable in said movable member attendant tocompressing any fluid between the members.

9. The invention according to claim 8, and a stop on the one side of themovable member limiting movement of the movable member toward thecylinder head and a fixed retainer mounted on the piston member on theother side of the movable member, said biasing means engaging saidretainer and said movable member in mg ing the latter to the stop.

10. The invention according to claim 6, and said biasing means includinga spring means urging the movable member away from the fixed member.

UNITED STATES PATENTS 3,028,019 4/1962 Settles et a1. 2138 3,218,05211/1965 Peterson 267.-1

DRAYTON E. HOFFMAN, Primary Examiner.

